These studies are directed at the cellular mechanisms by which stimuli cause the release of hormones and digestive enzymes and similar mechanisms which mediate the actions of hormones and neurotransmitters. The general focus is on how external stimuli interact with the cell membrane and activate intracellular control mechanisms which modulate physiological processes. A multidisciplinary approach is used involving electrophysiological, ultrastructural, pharmacologic techniques. The majority of the studies use the pancreatic acinar cell as a model for studying release of secretory product, although other studies are being carried out on brown adipose tissue, the adenohypophysis and the thyroid gland. Specific projects include: 1) Effects of ions on amylase release and measurement of ionic fluxes in pancreatic acinar cells, 2) Interactions of the calcium ionophore A23187 with isolated acinar cells, 3) Effects of cholinergic agonists and A23187 on pancreatic membrane potentials, 4) Effects of agents affecting microtubules and microfilaments on structure and secretion of the exocrine pancreas and thyroid gland, and 5) Electrophysiological studies on the adenohypophysis with emphasis on studying the effects of releasing hormones on identified cell types. BIBLIOGRAPHIC REFERENCES: Williams, J.A. Na ion dependence of in vitro pancreatic amylase release. Am. J. Physiology 229: 1023-1026, 1975. Williams, J.A. An in vitro evaluation of possible cholinergic and adrenergic receptors affecting pancreatic amylase secretion. Proc. Soc. Exp. Biol. Med. 150: 513-516, 1975.